Solar energy collector

ABSTRACT

The solar energy collector concentrates the sun&#39;s rays on a liquid medium that is used to power a mechanical energy device such as a positive displacement steam engine. A reflective surface of the solar energy collector is made from an arcuate portion of a circle having a trough-like surface to reflect and concentrate the sun&#39;s rays in a plane. A collector having a liquid medium flowing therethrough is located in the plane. The collector is constructed to extend across the entire plane for complete absorption by the liquid medium of the sun&#39;s rays reflected from the reflective surface. The collector and reflective surface are connected together for pivotal movement by an appropriate tracking apparatus so that the sun&#39;s rays are continually reflected during normal daylight hours through the plane in which the collector is located.

BACKGROUND OF THE INVENTION

This invention relates to a solar energy collector and, moreparticularly, to a solar energy collection system wherein the reflectoris formed from an arcuate portion of a circular cylinder trough-likesurface to reflect the sun's rays through a plane in which a collectorhaving a suitable fluid medium flowing therethrough is located. Thefluid medium heated by the sun's reflected rays is used to drive amechanical energy device. An appropriate tracking mechanism is used tocontrol pivotal motion of the reflector and collector so that the sun'srays continually reflect from a reflective surface through the plane inwhich the collector is located.

BRIEF DESCRIPTION OF THE PRIOR ART

Prior to the present invention, many systems have been devised for theutilization of solar energy as a source of power. Of the prior systemsutilizing a reflective surface for concentration the sun's rays, thereflective surface normally had a parabolic trough-like surface thatreflected the sun's rays along a focal line. These prior devices spentconsiderable time and effort to accurately locate the focal line bydetailed, expensive reflective surfaces. The forming of the reflectivesurface by bending of reflective material so that the sun's rays wouldreflect along a focal line was very difficult and expensive. Othermethods of forming the reflective surface were equally difficult andexpensive. It was very critical that the absorption device be accuratelylocated along the focal line. Therefore, prior solar energy collectorsthat utilized parabolic trough-like surfaces were not only veryexpensive to manufacture, but were also hard to maintain under normalenvironmental conditions because of the accuracy required.

In U.S. Pat. No. 3,868,823, a series of reflective slats were arrangedalong an arcuate, trough-like surface to reflect the sun's rays to afocal line. Such a configuration is expensive because each individualslat must be accurately positioned to reflect the sun's rays along thefocal line. A conduit carrying the fluid medium to be heated was locatedalong the focal line. The conduit was continually moved to maintain theconduit along the focal line.

Many other types of solar energy collectors that do not use aconcentration of the sun's rays by reflection have been devised and usedin the past; however, these devices do not produce the high temperaturesnecessary for the proper utilization of the sun's energy.

SUMMARY OF THE INVENTION

The present invention uses an arcuate portion of a cylinder forming atrough-like reflector for reflecting and concentration the sun's raysthrough a plane. In the plane is located a collector which abosrbs thesun's energy. The collector includes a conduit for flowing a suitablefluid medium therethrough (such as water). The entire collector isrigidly mounted to the supporting structure which also supports thereflector. If the conduit is not large enough to encompass the entireplane, suitable heat conductive material may extend outward from theconduit to properly absorb all of the sun's reflected rays. Insulationmaterial around the conduit reduces heat loss by the fluid medium.

The collector and reflector are mounted on common supportingsuperstructure so that they may be pivoted together. The superstructureis particularly designed to rest on the earth's surface and to pivot onthe supporting rockers for the reflector. Pivotal motion of thereflector and collector is controlled by a light detection device withsuitable control mechanism for driving a motor. The motor is connectedto the supporting superstructure by pulling cables and counterweights tosimultaneously pivot the reflector and collector thereby maintaining thecollector in the plane of the sun's reflected rays.

If the fluid medium used is water, it will vaporize in the collector andfeed to an engine such as a piston operated steam engine. The pistonoperated steam engine transforms the energy from the steam intomechanical energy for work. A storage tank is used for collecting thecondensed water from the steam engine for subsequent recirculationthrough the collector.

The reflective surface of the present invention is particularlyeconomical to build because the skeleton frame (previously referred toin general as superstructure) supporting the reflective surface is madefrom standard steel pipe bent along the radius of a circle. Thereflective surface attached to the steel pipe may be standard sizesheets of galvanized metal having a reflective film. The collector isalso made from standard inexpensive components, such as sheet metal,heat absorbing metal, conduit, protective glass and sheet insulationmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative, perspective view of the solar energycollector being used as a source of power.

FIG. 2 is a perspective view of the solar energy collector duringassembly with portions cut away to better illustrate construction.

FIG. 3 is a cross sectional view of FIG. 2 along section lines 3--3.

FIG. 4 illustrates the reflection of the sun's rays from an arcuatesurface when the sun is directly overhead.

FIG. 5 is an enlargement of FIG. 4 inside of circle 5 to illustrateconcentration of the sun's rays in a plane.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown a solar energy collector systemrepresented generally by the reference numeral 10. The solar energycollector system 10 has a circular arc shaped reflective surface 12formed in two parts that both reflect the sun's rays to a collector 14.A fluid medium (normally water) flows through the collector 14. If wateris used, the water is evaporated and used to drive a positivedisplacement steam engine 16. Water condensed into the positivedisplacement steam engine 16 is collected in tank 18 and recirculatedthrough the collector 14.

A standard light sensing mechanism 20 is used to detect the sun's rays.When the sun is not directly overhead, the light sensing mechanism 20will connect the motor 22 to a source of electric power (not shown). Inresponse to a control signal from the light sensing mechanism 20, themotor 22 will reposition the solar energy collector system 10 by meansof gear 24 on drive shaft 26 that connects to gear 28 via chain 30. Gear28 is rigidly connected to conduit 32, which conduit 32 is pivotallysupported through T-connectors 34 of posts 36. Also rigidly connected toconduit 32 are spools 38. Drive cables 40 are connected to the oppositeside of the skeleton frame 42 which supports the reflective surfaces 12.A portion of the drive cables 40 is wound on spools 38 with the endsbeing anchored thereto.

Counterweights 44 are connected through counterweight cables 46 to theopposite of the skeleton frame 42 from the connection by drive cables40. The counterweights 44 are supported by post 48 via pulleys 50. Thepulleys 50 are free to rotate in response to movement of counterweightcables 46 therethrough.

Referring now to FIG. 2 of the drawings, details of the construction ofthe solar energy collector system 10 is shown in more detail. Theskeleton frame 42 has a series of rockers 52 made from standard steelpipe bent along the arc of a circle. Each of the rockers 52 is connectedtogether by horizontal cross-support bars 54, 56, 58 and 60. Connectionbetween the rockers 52 and horizontal cross-support bars 54, 56, 58 and60 may be by any suitable means, such as welding. The horizontalcross-support bars 54, 56, 58 and 60 may be made from any suitablematerial, such as standard steel pipe. The horizontal cross-support bars54, 56, 58 and 60 do not extend above the rockers 52 so that a truearcuate plane is provided by the upper surfaces of rockers 52.

Though the spacing of the rockers 52 and the horizontal cross-supportbars 54, 56, 58 and 60 may vary, in this preferred embodiment they havebeen specifically designed so that a standard 4 × 10' sheet of 22 gaugegalvanized metal may be attached thereto. Because of the flexibility of22 gauge sheet metal, the sheet metal 62 bends along the same arc asrockers 52. Thereafter, the sheet metal 62 is connected by anyconvenient means, such as screws or welding, to rockers 52 as can beseen in FIG. 2. Also, the standard size sheet metal 62 may connect byconventional means along the edges of its longitudinal axis tohorizontal cross-support bars 54, 56, 58 and 60. This provides a veryrigid structure for the reflective surfaces 12, which reflectivesurfaces 12 may have a reflective film applied thereto. This process isrepeated until the entire skeleton frame 42 is covered with standardsize sheet metal 62 to form the reflective surfaces 12 as previouslyshown in FIG. 1.

Extending upward from the rockers 52 between horizontal cross-supportbars 56 and 58 are struts 64. The struts 64 may be connected by anysuitable means, such as welding, and may be formed from any suitablematerial, such as steel pipe. Each of the struts 64 are of the samelength and have a U-shaped support 66 attached to the upper end thereof.The U-shaped support 66 supports a heat absorbing conduit 68 which fitsin support 66. The heat absorbing conduit 68 must be made from a heatconductive material that will readily absorb and transfer energy to thefluid medium flowing therethrough.

Since the heat absorbing device 68 in this preferred embodiment does notcover the entire plane through which the sun's rays are reflected (whichwill be described in more detail subsequently in conjunction with FIGS.4 and 5) heat conductive sheet metal 70 is located above heat absorbingconduit 68 and is resting thereon as shown in FIG. 3. The heatconductive sheet metal 70 has an upper bend of approximately 90° so thatit drapes downward on either side of the heat absorbing conduit 68. Theheat conductive sheet metal 70 has lower inward flanges 72 forsupporting plate glass 76. The heat conductive sheet metal 70 musttransfer heat received from the sun's rays to the heat absorbing conduit68 by any suitable means. While the heat conductive sheet metal 70 maytransfer heat by direct contact with the heat absorbing conduit 68, thepreferred method of construction would include attachment of the sheetmetal 70 to the heat absorbing conduit 68 by any suitable means forbetter heat conduction. One method of attachment would be to bond thesheet metal 70 to the heat absorbing conduit 68 by a heat conductiveadhesive. To prevent energy losses due to wind or other environmentalfactors, sheet insulation material 74 is placed on the upper surfaces ofthe heat conductive sheet metal 70. Also to prevent energy loss, plateglass is held into position by lower inward flanges 72 of the heatconductive sheet metal 70 with the plate glass located below the heatabsorbing conduit 68 between each of the supporting struts 64.

To hold the sheet insulation material 74 securely into position, straps78 are secured at intervals along the heat absorbing conduit 68. Itshould be realized that the insulation material 74 may be held intoposition by other means, such as

On each end of the heat absorbing conduit 68 is located an appropriatefitting 80 for connection to flexible conduit 82 as shown in FIG. 1.Because the flexible conduit 82 must withstand high pressure, a steelbraided reinforced flexible conduit has been found to be particularlysuitable for these conditions. The flexible conduit 82 connects by meansof valve 84 and conduit 86 to the positive displacement steam engine 16.A relief valve 88 is provided to prevent pressures in excess of apredetermined amount. From the steam engine 16, condensed water andvapor feeds through conduit 90 to the storage tank 18. From the storagetank 18, water feeds back through conduit 92 to the heat absorbingconduit 68. To prime the system, it may be necessary to include a smallpump along conduit line 92 to start water flow through the heatabsorbing conduit 68. The mechanical energy from the steam engine 16 maybe used to drive any particular load or perform work. A typical suchexample would be the use of steam engine 16 to operate a water well forirrigation.

It should be understood that the overall system shown in FIG. 1 is forillustrative purposes to show an operative system. Other items notshown, but may be included for greater efficiency, could be a condenserand vacuum pump after the engine 16 and a pump (commonly called a boilerfeed pump) between the tank 18 and heat absorbing conduit 68. Also, itmay be desirable to have the heat absorbing conduit 68 (sometimes calleda water tube boiler) feeding into a surge tank or dome-shaped steamdrum, which may also function as tank 18.

To allow for remote operation of the solar energy collector system 10,the engine 16 may also operate a generator (as well as perform otherwork), which generator would supply electric power necessary to operateany other motor, pumps, etc. of the system. The generator may charge abattery to provide energy during start-up as well as operatingconditions.

Naturally, the heated fluid medium (normally steam) created via the heatabsorbing conduit 68 may be used for other forms of energy, such ascommercial heating or cooling.

Referring now to FIG. 4 of the drawings, there is shown a crosssectional view of an arcuate surface 96 with the sun's rays locateddirectly thereabove. Arcuate surface 96 has a radii R about point F. Atall places in this patent application, when the words "arc" or "arcuate"are used, they are referring to a portion of a circle. Considering onlythe portion of the arcuate surface 96 that is located 221/2° on eitherside of the perpendicular axis A, it can easily be seen that the sun'srays are reflected through a plane represented by dotted line 98. Thereflected sun's rays do not converge on a single focal point. Anenlargement of the area including the plane 98 is contained in FIG. 5,which enlargement is the area included in Circle 5 of FIG. 4. Aconservative estimate of the concentration of the reflected sun's raysfrom the arcuate surface 96 to the plane 98 would be a factor ofapproximately 30 to 1. Under good conditions, a concentration factor of45 to 1 can be obtained. Therefore, any heat absorbing device located inplane 98 would receive approximately 30 times the sun's rays as would bereceived from direct radiation.

Through calculations and experimentation, applicants have determinedthat if the sun's rays are perpendicular to the center tangent of thearc of reflective surface 12, the most desirable location for plane 98is between 0.4 and 0.5 R above the bottom of the arc of the reflectivesurface 12. In the preferred embodiment, the plane 98 is located atapproximately .46 R.

In the solar energy collector system 10, all of the sun's rays for adistance of approximately 22 1/2° on either side of the struts 64 (withthe exception of the small opening 100 along the middle of thereflective surface 12) will be concentrated in a plane where thecollector 14 is located. In the present invention, since the collector14 should be located in an entire plane and not along a single focalline, a much greater degree of latitude in construction is permissible.Also because the reflective surfaces 12 are arcuate (not parabolic), thesolar energy collector system is much simplier, easier and economical toconstruct. The conductive sheet metal 70 located around heat absorbingconduit 68 may not be necessary for absorbing the reflected rays if theheat absorbing conduit 68 covers the entire reflective plane. If not,heat conductive sheet metal 70 may be necessary to insure that all ofthe reflected energy from the sun is properly transmitted to the fluidmedium.

To securely hold the collector 14, including the heat aborsbing conduit,in position during pivotal motion of the solar energy collectorsystem,tension cables are connected between the collector 14 and theskeleton frame 42 as shown in FIG. 1. Also, the small opening 100 in thereflective surface 12 has certain design advantages. Any residue such asdust on the reflective surface 12 may be washed off by rain or by awater hose. When the reflective surface 12 is pivoted to directlyreceive the sun's rays during early morning or lateafternoon, windresistance is reduced by the wind flowing through small opening 100. Theinclusion of the small opening 100 does not reduce the total reflectivesurface 12 of solar energy collector system 10 because the area of smallopening 100 is shaded by the collector 14.

We claim:
 1. A solar energy apparatus for concentrating the sun's rayson a fluid medium comprising:arcuate, trough-like reflector means forreflecting and concentrating the sun's rays through a plane fixed withrespect to said reflector means; collector means located in said plane,said collector means providing conduit means for said fluid medium, saidcollector means being heated by the sun's reflected, concentrated raysin said plane; stationary support means on each side of said reflectormeans, said stationary support means having line means connected toopposite sides of said reflector means via pulley means, motor means forturning said pulley means to adjust said reflector means with said linemeans to maintain said sun's rays perpendicular to a line tangent to thecenter of said reflector means.
 2. The solar energy apparatus of claim 1including structure means extending above said reflector means torigidly hold said collector means in said plane, counterweight meansconnected through at least one of said pulley means for applying a forceto one side of said reflector means which force may be overcome by saidmotor means.
 3. The solar energy apparatus of claim 2 wherein saidcollector means comprises an elongated tubular conduit, said conduithaving flange means continguous thereto and coextensive therewith, saidflange means extending outwardly on the sides of said conduit means toencompass said fixed plane.
 4. The solar energy apparatus of claim 3wherein said flange means includes a cover draped over said tubularconduit and bonded thereto, upper surfaces of said cover being coveredwith insulation means, glass means being suspended below said covermeans and said tubular conduit.
 5. The solar energy apparatus of claim 2wherein said structure means includes arcuate rocker supports for saidreflector means, said rocker supports providing a pivot surface for saidreflector means.
 6. The solar energy apparatus of claim 5 wherein saidstructure means extends upward to support said collector means, saidstructure means being from standard metal pipe.
 7. A solar energy systemfor utilizing the sun's rays to generate power comprising:frame means;reflector means having an arcuate, trough-like reflective surfacemounted on said frame means; collector means mounted on said frame meansin a plane above said reflective surface, said plane being fixed withrespect to said reflective surface, said collector means providing aheat absorbing conduit extending therethrough; a fluid medium forflowing through said heat absorbing conduit, said fluid medium beingheated in said conduit; engine means receiving said heated fluid mediumthrough flow means, said engine means generating mechanical energy fromsaid heated fluid medium, said fluid medium being collected and returnedto said heat absorbing conduit by said flow means; stationary supportmeans adjacent to said frame means, said stationary support means havingline means connected to opposite sides of said frame means via pulleymeans, motor means for turning said pulley means to adjust said framemeans and reflector means with said line means to maintain said sun'srays perpendicular to a line tangent to the center of said reflectormeans; counterweight means connected through at least one of said pulleymeans for applying a force to one side of said frame means which forcemay be overcome by said motor means.
 8. The solar energy system of claim7 wherein said collector means includes flange means contiguous andcoextensive with said heat absorbing conduit means to encompass saidplane.
 9. The solar energy system of claim 8 wherein said frame meansincludes rockers of the same arcuate shape as said reflector means, saidrockers supporting said reflector means and providing structure on whichsaid motor means may pivot said reflective surface via said line means.10. The solar energy system of claim 7 wherein said reflector means hasa given radius of curvature, said plane being parallel to a second planetangent to the center of said reflective surface and between 0.4 and 0.5times the radius above said second plane.